The Kadic case built explicitly on the breakthrough made by Filartiga but raised additional questions which the earlier case had left undecided, namely, whether some violations of the law of nations may be remedied when committed by those not acting under the authority of a state and if so, whether genocide, war crimes, and crimes against humanity are among the violations that do not require state action.

The appeal court held that the law of nations, as understood in the modern era, does not confine its reach to state action. Certain forms of conduct when undertaken by individuals equally violate the law of nations. Citing The Restatement (Third) of the Foreign Relations Law of the United States (1986) the judges confirmed that piracy, war crimes and genocide are among those offences against international law for which individuals may be held responsible.

Adopting a rather broad definition of ‘state action’ the appeal court held that in any case the appellants were ‘entitled to prove their allegations that Karadzic acted under color of law of Yugoslavia by acting in concert with Yugoslav officials or with significant Yugoslavian aid’. (This aspect of the decision has attracted criticism – see our page of books and articles).